[PATCH] GIT: Listen on IPv6 as well, if available.
[git/git.git] / daemon.c
1 #include "cache.h"
2 #include "pkt-line.h"
3 #include <signal.h>
4 #include <sys/wait.h>
5 #include <sys/socket.h>
6 #include <netdb.h>
7 #include <netinet/in.h>
8
9 static const char daemon_usage[] = "git-daemon [--inetd | --port=n]";
10
11 static int upload(char *dir, int dirlen)
12 {
13 if (chdir(dir) < 0)
14 return -1;
15 chdir(".git");
16
17 /*
18 * Security on the cheap.
19 *
20 * We want a readable HEAD, usable "objects" directory, and
21 * a "git-daemon-export-ok" flag that says that the other side
22 * is ok with us doing this.
23 */
24 if (access("git-daemon-export-ok", F_OK) ||
25 access("objects/00", X_OK) ||
26 access("HEAD", R_OK))
27 return -1;
28
29 /*
30 * We'll ignore SIGTERM from now on, we have a
31 * good client.
32 */
33 signal(SIGTERM, SIG_IGN);
34
35 /* git-upload-pack only ever reads stuff, so this is safe */
36 execlp("git-upload-pack", "git-upload-pack", ".", NULL);
37 return -1;
38 }
39
40 static int execute(void)
41 {
42 static char line[1000];
43 int len;
44
45 len = packet_read_line(0, line, sizeof(line));
46
47 if (len && line[len-1] == '\n')
48 line[--len] = 0;
49
50 if (!strncmp("git-upload-pack /", line, 17))
51 return upload(line + 16, len - 16);
52
53 fprintf(stderr, "got bad connection '%s'\n", line);
54 return -1;
55 }
56
57
58 /*
59 * We count spawned/reaped separately, just to avoid any
60 * races when updating them from signals. The SIGCHLD handler
61 * will only update children_reaped, and the fork logic will
62 * only update children_spawned.
63 *
64 * MAX_CHILDREN should be a power-of-two to make the modulus
65 * operation cheap. It should also be at least twice
66 * the maximum number of connections we will ever allow.
67 */
68 #define MAX_CHILDREN 128
69
70 static int max_connections = 25;
71
72 /* These are updated by the signal handler */
73 static volatile unsigned int children_reaped = 0;
74 pid_t dead_child[MAX_CHILDREN];
75
76 /* These are updated by the main loop */
77 static unsigned int children_spawned = 0;
78 static unsigned int children_deleted = 0;
79
80 struct child {
81 pid_t pid;
82 socklen_t addrlen;
83 struct sockaddr_storage address;
84 } live_child[MAX_CHILDREN];
85
86 static void add_child(int idx, pid_t pid, struct sockaddr *addr, socklen_t addrlen)
87 {
88 live_child[idx].pid = pid;
89 live_child[idx].addrlen = addrlen;
90 memcpy(&live_child[idx].address, addr, addrlen);
91 }
92
93 /*
94 * Walk from "deleted" to "spawned", and remove child "pid".
95 *
96 * We move everything up by one, since the new "deleted" will
97 * be one higher.
98 */
99 static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
100 {
101 struct child n;
102
103 deleted %= MAX_CHILDREN;
104 spawned %= MAX_CHILDREN;
105 if (live_child[deleted].pid == pid) {
106 live_child[deleted].pid = -1;
107 return;
108 }
109 n = live_child[deleted];
110 for (;;) {
111 struct child m;
112 deleted = (deleted + 1) % MAX_CHILDREN;
113 if (deleted == spawned)
114 die("could not find dead child %d\n", pid);
115 m = live_child[deleted];
116 live_child[deleted] = n;
117 if (m.pid == pid)
118 return;
119 n = m;
120 }
121 }
122
123 /*
124 * This gets called if the number of connections grows
125 * past "max_connections".
126 *
127 * We _should_ start off by searching for connections
128 * from the same IP, and if there is some address wth
129 * multiple connections, we should kill that first.
130 *
131 * As it is, we just "randomly" kill 25% of the connections,
132 * and our pseudo-random generator sucks too. I have no
133 * shame.
134 *
135 * Really, this is just a place-holder for a _real_ algorithm.
136 */
137 static void kill_some_children(int signo, unsigned start, unsigned stop)
138 {
139 start %= MAX_CHILDREN;
140 stop %= MAX_CHILDREN;
141 while (start != stop) {
142 if (!(start & 3))
143 kill(live_child[start].pid, signo);
144 start = (start + 1) % MAX_CHILDREN;
145 }
146 }
147
148 static void check_max_connections(void)
149 {
150 for (;;) {
151 int active;
152 unsigned spawned, reaped, deleted;
153
154 spawned = children_spawned;
155 reaped = children_reaped;
156 deleted = children_deleted;
157
158 while (deleted < reaped) {
159 pid_t pid = dead_child[deleted % MAX_CHILDREN];
160 remove_child(pid, deleted, spawned);
161 deleted++;
162 }
163 children_deleted = deleted;
164
165 active = spawned - deleted;
166 if (active <= max_connections)
167 break;
168
169 /* Kill some unstarted connections with SIGTERM */
170 kill_some_children(SIGTERM, deleted, spawned);
171 if (active <= max_connections << 1)
172 break;
173
174 /* If the SIGTERM thing isn't helping use SIGKILL */
175 kill_some_children(SIGKILL, deleted, spawned);
176 sleep(1);
177 }
178 }
179
180 static void handle(int incoming, struct sockaddr *addr, socklen_t addrlen)
181 {
182 pid_t pid = fork();
183
184 if (pid) {
185 unsigned idx;
186
187 close(incoming);
188 if (pid < 0)
189 return;
190
191 idx = children_spawned % MAX_CHILDREN;
192 children_spawned++;
193 add_child(idx, pid, addr, addrlen);
194
195 check_max_connections();
196 return;
197 }
198
199 dup2(incoming, 0);
200 dup2(incoming, 1);
201 close(incoming);
202 exit(execute());
203 }
204
205 static void child_handler(int signo)
206 {
207 for (;;) {
208 pid_t pid = waitpid(-1, NULL, WNOHANG);
209
210 if (pid > 0) {
211 unsigned reaped = children_reaped;
212 dead_child[reaped % MAX_CHILDREN] = pid;
213 children_reaped = reaped + 1;
214 continue;
215 }
216 break;
217 }
218 }
219
220 static int serve(int port)
221 {
222 struct addrinfo hints, *ai0, *ai;
223 int gai;
224 int socknum = 0, *socklist = NULL;
225 int maxfd = -1;
226 fd_set fds_init, fds;
227 char pbuf[NI_MAXSERV];
228
229 signal(SIGCHLD, child_handler);
230
231 sprintf(pbuf, "%d", port);
232 memset(&hints, 0, sizeof(hints));
233 hints.ai_family = AF_UNSPEC;
234 hints.ai_socktype = SOCK_STREAM;
235 hints.ai_protocol = IPPROTO_TCP;
236 hints.ai_flags = AI_PASSIVE;
237
238 gai = getaddrinfo(NULL, pbuf, &hints, &ai0);
239 if (gai)
240 die("getaddrinfo() failed: %s\n", gai_strerror(gai));
241
242 FD_ZERO(&fds_init);
243
244 for (ai = ai0; ai; ai = ai->ai_next) {
245 int sockfd;
246 int *newlist;
247
248 sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
249 if (sockfd < 0)
250 continue;
251 if (sockfd >= FD_SETSIZE) {
252 error("too large socket descriptor.");
253 close(sockfd);
254 continue;
255 }
256
257 #ifdef IPV6_V6ONLY
258 if (ai->ai_family == AF_INET6) {
259 int on = 1;
260 setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY,
261 &on, sizeof(on));
262 /* Note: error is not fatal */
263 }
264 #endif
265
266 if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
267 close(sockfd);
268 continue; /* not fatal */
269 }
270 if (listen(sockfd, 5) < 0) {
271 close(sockfd);
272 continue; /* not fatal */
273 }
274
275 newlist = realloc(socklist, sizeof(int) * (socknum + 1));
276 if (!newlist)
277 die("memory allocation failed: %s", strerror(errno));
278
279 socklist = newlist;
280 socklist[socknum++] = sockfd;
281
282 FD_SET(sockfd, &fds_init);
283 if (maxfd < sockfd)
284 maxfd = sockfd;
285 }
286
287 freeaddrinfo(ai0);
288
289 if (socknum == 0)
290 die("unable to allocate any listen sockets on port %u", port);
291
292 for (;;) {
293 int i;
294 fds = fds_init;
295
296 if (select(maxfd + 1, &fds, NULL, NULL, NULL) < 0) {
297 error("select failed, resuming: %s", strerror(errno));
298 sleep(1);
299 continue;
300 }
301
302 for (i = 0; i < socknum; i++) {
303 int sockfd = socklist[i];
304
305 if (FD_ISSET(sockfd, &fds)) {
306 struct sockaddr_storage ss;
307 socklen_t sslen = sizeof(ss);
308 int incoming = accept(sockfd, (struct sockaddr *)&ss, &sslen);
309 if (incoming < 0) {
310 switch (errno) {
311 case EAGAIN:
312 case EINTR:
313 case ECONNABORTED:
314 continue;
315 default:
316 die("accept returned %s", strerror(errno));
317 }
318 }
319 handle(incoming, (struct sockaddr *)&ss, sslen);
320 }
321 }
322 }
323 }
324
325 int main(int argc, char **argv)
326 {
327 int port = DEFAULT_GIT_PORT;
328 int inetd_mode = 0;
329 int i;
330
331 for (i = 1; i < argc; i++) {
332 char *arg = argv[i];
333
334 if (!strncmp(arg, "--port=", 7)) {
335 char *end;
336 unsigned long n;
337 n = strtoul(arg+7, &end, 0);
338 if (arg[7] && !*end) {
339 port = n;
340 continue;
341 }
342 }
343
344 if (!strcmp(arg, "--inetd")) {
345 inetd_mode = 1;
346 continue;
347 }
348
349 usage(daemon_usage);
350 }
351
352 if (inetd_mode)
353 return execute();
354
355 return serve(port);
356 }